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The difference in the number of waves when yellow light propagates through air and vacuum columns of the same thickness is one. The thickness of the air column is _____ mm. [Refractive index of air = 1.0003, wavelength of yellow light in vacuum = 6000 Å]

1. 20
2. 30
3. 40
4. 50

Correct answer: 30

Solution

The difference in the number of waves is determined by the change in wavelength due to the refractive index. Given the refractive index of air and the wavelength of yellow light in vacuum, the thickness of the air column can be calculated to yield a difference of one wave, which corresponds to 30 mm.

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